Hundreds of millions of shopping carts are in use in supermarkets around the world. In typical use, the shopper fills the cart with goods in the store, empties the cart at the checkout counter, and then loads the goods into bags to take them home. The bags may be disposable, but reusable bags are coming into increasing use due to environmental pressures. For small quantities of goods, some shoppers use their own trolleys, which typically consist of a flexible sack mounted on a folding wheeled frame.